Numerous reasons may make the ability to accurately obtain a small representative sample of solid materials from a continuous flow process important. For example, the United States Environmental Protection Agency requires certain industries to maintain programs for monitoring various by-products and to demonstrate that the monitoring technology consistently and accurately obtains representative samples from the stream of material. Similarly, a manufacturer's own quality control program may require accurate sampling from a continuous flow process to determine whether the product meets quality standards. To obtain meaningful test results the sampling mechanism must be able to accurately obtain a representative sample of material from a continuous flow process.
In this regard, various devices for collecting a samples of material from a continuous flow process are well known and take numerous embodiments in the art. For example, U.S. Pat. No. 398,275, issued to Palmer, discloses an apparatus for sampling ores including a cone positioned in the flow of the material for directing the flow of material across the surface of the cone and a plurality of splitters for removing a sample of the material. Similarly, U.S. Pat. No. 518,915, issued to Clarkson, discloses a device for sampling flowable solid material from a stream thereof using a series of staged funnels with the lowermost funnel having chutes for removing a portion of the material from the stream.
Numerous other devices for collecting samples from a continuous stream of flowable solids have been disclosed, most of which require positioning within a stream of flowable solids a device having a plurality of chutes for directing a portion of the stream away from the principal flow thereof. However, a common problem with existing sampling devices is the tendency for the flowable solids to block the chutes which direct a sample of material away from the principal material flow. The blocking becomes particularly acute when attempting to sample fine granules or powders, such as cement dust, which exhibit the behavior of sticking to the side walls and sloped floor of the chutes. The geometry of the chutes used with the apparatus frequently contributes to a tendency of particles to build up to the point where they block chutes.
The angle of repose is the maximum angle at which a flowable solid material will remain at rest on a given surface. The angle of repose depends upon characteristics of the flowable solid including the density, the specific gravity, the moisture content, and the particle size distribution. If the sloped floor of the chute is not angled at least equal to or greater than the angle of repose of the material being sampled the material will tend to build up on the floor of the chute causing the chute to become blocked. Additionally, most existing chutes employ straight side walls defining a uniform cross sectional width within the chute. When material begins to build up on the floor of the chute it reduces the cross-sectional area of the exit path, thereby impeding the flow of solids out of the chute and contributing to the blocking of the chute. This blocking may reduce the ability of the device to obtain accurate, reliable samples from the stream. Accordingly, there is a need in the art for a device for accurately and reliably collecting samples from a continuous stream of flowable solids. More particularly, there is a need in the art for a sampling device which is less susceptible to blockage which may hamper the accuracy of the sampling device.